The invention relates to a color cathode-ray tube (CRT) and more particularly to the frame/mask device for selecting colors placed inside the glass envelope of the tube. The invention is applicable to any type of tube comprising a color selection mask and is more particularly suited to tubes whose mask is held under tension by the frame to which it is fastened.
Conventional cathode-ray tubes comprise a color selection mask located at a precise distance from the inside of the glass front face of the tube, on which front face red, green and blue phosphor arrays are deposited. Color CRTs generally have three electron beams, each one corresponding to a particular primary color phosphor array. The mask makes it possible for each particular beam to illuminate only the phosphor of the corresponding color.
During operation of the tube, the color selection mask must be placed and held in a precise position inside the tube. The function of holding the mask is carried out by means of a generally rigid rectangular metal frame, to which the mask is welded. The frame/mask assembly is mounted in the front face of the tube by a suspension means which includes a spring having an aperture. The aperture is designed to engage with one of the metal pins included in the glass front face. Generally tubes manufactures have the support means either on the sides of the mask frame or at the corners of the frame.
The current trend in the CRT industry is toward increasingly flat front faces. To produce tubes, manufactures have designed mask having flatter contours. The meet the demand for flatter mask contours the some designers have designed uniaxial tension masks. Such structures are described, for example, in U.S. Pat. No. 5,111,107. To keep the mask flat, high tension must be applied. The high tension requirement has forced designers to construct relatively heavy frame structures which consumes much material. As such, there is a need in the industry to develop lighter structures that can also effective hold a mask under tension.
The invention is for a CRT that comprises a tension mask having light frame structure. The light frame structure is realized reinforcing means for the frame/mask system. The CRT according to the invention also includes a glass front face on which a phosphor screen is deposited, a color selection mask placed close to the screen, a frame to which the mask is attached and which holds the mask under tension in at least one direction, the frame being of substantially rectangular shape defined by a pair of opposed long side and a pair of opposed short sides. At least two opposed sides each comprise an edge in the form of a metal plate substantially parallel to the surface of the mask. The frame/mask assembly is held inside the front face by reinforcing means cooperating with pins inserted in the sidewalls of the front face. The CRT is further characterized by reinforcing means having a metal plate fastened to at least one of the sides, close to the corners of the frame, wherein the plates comprise a longitudinal dimple lying at least partially in the direction of tension of the mask.